Images of sun may help solve mystery

NEW YORK -- New, detailed images of the fiery arches of gas in the sun's outer atmosphere might help solve a decades-old mystery: How can the atmosphere be so much hotter than the sun's surface?

The images released Tuesday by the National Aeronautics and Space Administration don't reveal the answer, but experts say they do overturn one longstanding idea about where the heating takes place.

Scientists have known for decades that the outer atmosphere, called the corona, is heated to around 3 million degrees -- much hotter than the visible surface of the sun, which is only about 10,000 degrees.

Researchers also knew that the corona contains millions of arches of extremely hot gas reaching up from the surface as far as 200,000 miles, but that didn't tell them where the heat was coming from. The standard belief was that the coronal loops were being heated all along their lengths.

Not so, according to the new ultraviolet light images from NASA's Transition Region and Coronal Explorer spacecraft. The images indicate the heat is being applied near the bottom of the arches, within about 10,000 miles of the sun's visible surface.

The source of that heat remains a mystery, but knowing the location should help scientists figure it out.

''It gives us some kind of handle as to what might be going on,'' said Spiro Antiochos of the Naval Research Laboratory in Washington, D.C., who is familiar with the results. ''This is brand new information .... It is very important.''

The images show the arches in great detail, somewhat like revealing individual trees where scientists had only seen a forest.

They show that each arch is actually a bundle of thin, individual strands of gas.